Circular economy Chemical recycling of polycarbonate reaches important milestone

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Plastics manufacturer Covestro has developed a new process for recycling polycarbonate, i.e. multi-chain plastics. In this process, plastics are converted back into their monomers, i.e. a precursor of plastics, so that they can be fed back into the production process as alternative raw materials.

Covestro is starting the technical implementation of chemical recycling on a pilot scale at its site in Leverkusen. On the way to industrial scale, the process is to be optimised and undergo further development stages.

The return of plastics through recycling replaces primary fossil raw materials in production. According to Covestro's plans, comprehensive recycling will contribute to climate neutrality and the protection of natural resources and the environment. Mechanical recycling of polycarbonate is already an important component of the company's recycling strategy. Mechanical recycling is always used when waste streams are sufficiently unmixed and the recycled polycarbonate meets the requirement profile of the future application.

Chemical recycling works in a complementary way to mechanical recycling — it converts plastic building blocks back into monomers, i.e. their individual building blocks. These can be separated and serve as raw materials for future plastics. Chemical recycling can therefore make larger waste streams, which are particularly unsuitable for mechanical processes, accessible for recycling; it allows the production of plastics that meet the highest quality requirements. Covestro is therefore actively developing chemical recycling.

Chemolysis can directly close the polycarbonate cycle

The newly developed process, which was advanced by an international team, is a specific chemolysis process adapted to polycarbonate. “Pre-sorted waste streams containing a product content of more than 50 % polycarbonate can be recycled in this way. This has been successfully demonstrated with various polycarbonate-containing plastic wastes,” explains Markus Dugal, Head of Process Technology at Covestro. “With the help of this chemolysis, the cycle can be closed to a direct precursor of polycarbonate. This makes the recycling process very sustainable.”

Direct use of recycled product as raw material possible

The recycled product, a precursor of polycarbonate, can be mass-balanced and reused as a raw material for the production of polycarbonate without further processing. “Such high-quality recycled raw materials are needed for applications that require top quality. These are, for example, applications in the automotive sector with special demands on safety, optical transparency or aesthetics. Or products in our digital everyday life, such as consumer electronics,” says Lily Wang, Head of the Business Entity Engineering Plastics.

Investment in the millions

After successful development in the laboratory, the next stage of development, the technical implementation of a continuous process, has already begun. A pilot plant, which is currently in the planning stage, will be used to gain experience that will be necessary for further expansion to industrial scale. Millions of euros will be invested in this over the next few years. The pilot plant will be built in Leverkusen, Germany.

At the same time, Covestro is driving forward further processes for innovative recycling of polycarbonate in its research laboratories. These include chemolytic alternatives, recycling with enzymes that break down the plastic, and smart pyrolysis. Promising alternatives will also be piloted.

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